1. Field of Invention
The present invention relates to the field of marine seismic equipment and methods of using same in obtaining marine seismic data. More specifically, the invention relates to methods for reducing streamer and/or source steering during time periods of recording seismic data and/or generating seismic signals to improve seismic data quality.
2. Related Art
Marine seismic exploration investigates and maps the structure and character of subsurface geological formations underlying a body of water. For large survey areas, seismic vessels may tow one or more seismic sources and multiple seismic streamer cables through the water. The streamers may be positioned using controllable steerable birds, deflectors, steerable buoys, and the like. During the time period of actually recording marine seismic data by acoustic receivers integrated into or attached to a streamer, it is a goal of marine seismologists to reduce noise, or increase the signal-to-noise ratio. In certain multicomponent streamers it is critical that the orientation of the two axes making up the vertical plane be known to allow data processing operations to adequately de-ghost the seismic data. Knowledge of the orientation of these axes would also benefit other data processing activities, such as interpolation of received seismic data, wavefield interpretation, data filtering, particle motion data analysis, and the like. “Ghosting” and “deghosting” of marine seismic data are well-known terms of this art. Presently, no interruptions of streamer or source steering actions are undertaken due to data recording considerations, as in theory the streamers and sources will be in the best positions for recording data. (In certain embodiments in practice today, sources may include one or more hydrophones in order to check the quality of the source signal(s), and this is known as a calibrated marine seismic source, or CMS. This is sometimes referred to as the “near field signature.” Up/down signal decomposition has been achieved previously with over/under sources and over/under streamer data acquisition.
It would be an advance in the art if methods for controlling streamer and/or source orientation could be devised using reduced steering during time periods of recording seismic data and/or generating seismic signals to improve marine seismic data quality.